Generally a medium fill of a washing machine is adequate for the load being washed. If the user selects a high or extra high fill the tendency is to forget to reset to a lower fill on subsequent cycles, thus wasting hot water. It is desired to have the pressure switch automatically reset to medium on completion of a cycle in which high or extra high has been selected.
The pressure switch uses a multi-lobed cam for selecting the various water levels (the lobes between each setting serving to positively reset the switch). To drive such a cam requires considerable force and this suggests two approaches. The first would be a solenoid which is fast acting but to get enough force and stroke a large solenoid would be required and thus becomes too costly.
A large force and stroke can be obtained with a heated wax motor but that sort of device operates too slowly for serious consideration. A different approach is dictated.
The problem is new and no prior art is known.